The advent of modern production facilities mandated the development of various valve apparatus susceptible to incorporation into mechanized and automatic equipment. Accordingly, there has been substantial development of a wide variety of valves, valve apparatus and systems which may be employed in automated processing equipment to dispense metered quantities of materials, among which are included solid, liquid and even gaseous materials. One of the more difficult problems facing the dispensing industry has been and remains the metered dispensing of viscous materials. These materials, while flowable, are difficult to handle. A particular problem resides in the dispensing of viscous materials since, due to their relatively high surface tension, the materials tend to cling together and to the dispensing equipment with which they are associated.
Examples of viscous materials for which accurate dispensing has value may be found in the food industry and include such viscous products as butter, peanut butter, jellies, cheeses, to name a few. In the cosmetic industry, these viscous materials may include thick lotions, gels, creams and the like. Household chemicals include such diverse products as shoe polish, greases, hand cleaners, and industrial chemicals include greases and other petroleum products, sealants, adhesives, and a host of others. All of these industries experience difficulties with automated packaging equipment, and the present invention is directed to providing improved dispensing techniques.
There has been in the past a reasonable degree of development of dispensing valves, apparatus and systems for dispensing viscous materials, of the types noted above. One example of a metering valve apparatus used in the food industry is shown in U.S. Pat. No. 2,649,996 issued 25 Aug. 1953 to Harrington. Here, a dual dispensing valve system employs specially constructed piston heads as part of the valve structure to produce a section at the end of respective dispensing nozzles so that material clinging to the end of the nozzle is drawn back into the valve or discharge conduit. Other examples of valve systems in the food industry which utilize the "snuff-back" feature to reduce spillage or dripping are shown in U.S. Pat. No. 3,731,716 issued 8 May 1973 to Darish and U.S. Pat. No. 3,717,284 issued 20 Feb. 1973 to Gerrard.
Despite the improvements in technology represented by these structures, there remains a need for improved valves, apparatus and systems incorporating a "snuff-back" feature. There is a further need for efficient, simplified valve structures which are simplified in configuration and are thus relatively low in cost to manufacture, economical to maintain, and durable in use.